Here is the horn calculation. I actually planned to use it from 3 kHz up (or what the large multicell permits). I have a feeling it is too small for 1.5 kHz.
Pano, your size estimates are correct, the STL is in milimeters, maybe the printing service did not use milimeters? It is really small, the mounting holes distance is 76 mm. I am not sure if it is even printable, maybe it will need a little support inside the throat.
It was more or less just a proof of concept if I would be able to make one. Version 2 with some input of the experts can be put together quite quickly.
Pano, your size estimates are correct, the STL is in milimeters, maybe the printing service did not use milimeters? It is really small, the mounting holes distance is 76 mm. I am not sure if it is even printable, maybe it will need a little support inside the throat.
It was more or less just a proof of concept if I would be able to make one. Version 2 with some input of the experts can be put together quite quickly.
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I would like to design a new 3D model for a mini multicell, that would fit the Prusa Mini, which is 180x180x180 mm print volume. It would be for a 1" driver with standard 2 bolt mounting pattern and I will of course share the model here. Given these constraints, how should the horn to look like? How many cells (max 5x3), cell size and flare should be chosen? It should be usable as a tweeter horn. GM and Pano, your input would be highly appreciated.
1) Sorry, but I currently no longer have the time to manually input anyone's sims to view nor any other [software] currently, so please attach the [txt] file of any HR sims you wish me to view and/or any other type document I can view on freeware online.
2) Recommend starting with 'attaching' your horn to a TAD2001's measured specs [attached], noting that the S1/S2/CON is the tiny conical horn inside it that from dim memory/IIRC constitutes the ~ 3500 Hz - up BW if like Lansing/Altec's 800 series 1" CDs.
So basically a max 18 x 18 cm o.d. terminus/mouth [Sm] x 18 cm o.d. axial length [lx].
[18^2*4/pi]^0.5 = ~20.32 cm dia./2*0.613 = ~6.23 cm 4pi end correction + ~72 = ~78.23 cm acoustic terminus/mouth [Sm'] = ~34400/78.23 = ~439.76 Hz [Sm'] cut-off.
34400/4/18 = ~477.78 Hz axial cut-off with its acoustical cut-off [lx'] a function of the horn's flare factor [expo, etc.]
So a good [Forrest Gumpesqe] 'rule-of-thumb' [ROT] is 'square is as square does' in horn design. 😉
I would go with 6 cells. At 18cm wide, those cells just aren't going to beam that much, so no need for 15 inside that 324 cm2 mouth area.
+1 Forgot to answer; except for looks, if [6] was good enough for the various Altecs, good enough for me. Then again, at [15] it would be somewhat resistive, so might be worth it from a horn loading SQ POV same as the [18] multi-cells at 300 Hz and especially those lovely 'little' Jensen 30+ 500 Hz multi-cells.
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Thanks for the input, gentlemen. I will play around a bit with Hornresp and will attach the record next time, the screenshot was just informational. Would it be of any advantage to make a 3x3 pattern?
GM makes a good point about more cells being resistive, which might have sonic benefits.
Six cells seems like enough to spread the HF. An exponential horn that is 170mm wide by 170mm deep should have a beam width of around 75 degrees at 3 kHz, your crossover frequency. The beam has narrowed to half that circa 13 kHz and is at 30 degrees up at 18-20 kHz. Not bad, but you want better. This should be somewhat driver dependent.
Divide that 75 degree coverage into 3 cells wide and we see that each cell needs to cover 25 degrees. That should not be a problem for cells this small, about 28mm wide.
Six cells seems like enough to spread the HF. An exponential horn that is 170mm wide by 170mm deep should have a beam width of around 75 degrees at 3 kHz, your crossover frequency. The beam has narrowed to half that circa 13 kHz and is at 30 degrees up at 18-20 kHz. Not bad, but you want better. This should be somewhat driver dependent.
Divide that 75 degree coverage into 3 cells wide and we see that each cell needs to cover 25 degrees. That should not be a problem for cells this small, about 28mm wide.
It is printable🙂 Here on a DE500. It only needed a bit of work with a needle file on the inner edges - there are some overhangs that do not print 100% correctly. Measurements will follow later when I have some other stuff printed for a measurement session.
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Now it is also on Thingiverse: Baby Multicell horn for 1" compression drivers by pelanj - Thingiverse
Not yet, I had time only for one or two sweeps for each project. This one is small enough to make a full set of polars in my living room - cannot tell when that will be unfortunately.
I'm looking forward to seeing what you measure (since I can't hear them). Will the multicell show its supposed advantage of axis?
Finally, just a quick set up for a short listening test. Crossover points 450 and 4500 Hz. The spatial arrangement is far from optimal, but the coverage seems to be quite wide and it is at least as good as the EAW cinema horn with DE72 I used for the other channel. The midrange horn has a certain appeal. Both sides were level matched and very roughly equalised flat.
Edit: I added a sweep at the listening position in room. Both multicell horns deserve more attention and measurement outside. That will be done when the weather permits (March / April soonest I am afraid).
Edit: I added a sweep at the listening position in room. Both multicell horns deserve more attention and measurement outside. That will be done when the weather permits (March / April soonest I am afraid).
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